Genus: Charina - Derived from Greek
"graceful".Species: bottae - Named after Paolo Emilio
Botta, an Italian explorer serving aboard the ship Heros as doctor, visited
California in the 1820's, and published his book Observations on the
Inhabitants of California.

Physical Description

Rubber boas are one of the smallest members of the boa family, and one of the
northern most ranging. Adults are generally a uniform color dorsally, ranging
from tanned leather brown (southern population are almost always light tan),
olive brown, medium brown, to a dark chocolate brown.1. Their ventral surface (belly) is most often a light yellow with brown
mottling in some adults. Babies are born pink and slightly transparent, and
gradually darken with age. Color variations occur between AND within each
locality. In the Pacific Northwest, adult males generally reach an average
length of about 21 inches, with the females slightly longer - on average 26
inches. Adults from different regions may vary slightly, such as the Southern
Rubber Boa (C. b. umbratica), the smallest subspecies, where males typically max
out at 18 inches, and females at 22 inches.2
See Photos Page for photos of colors and
variations.

Life Span

RAAB Mill site female #1 was found, surveyed, and released by Richard Hoyer
in 1971. Over many years she was found over and over again, until finally kept
and retained in captivity. Thirty years later she is still alive. When first
found she was an adult with extensive scarring. Extrapolation of likely age at
time of capture based on growth rates of other wild Rubber Boas from the same
locality indicate that she was at minimum 15 years old, and likely more than 20+
years old.3 In the year 2001 she turned
at least Fifty years old! And possibly as much as 70!! More than half of her
life was spent in the wild, with the remainder in captivity. She produced a
litter of young in the summer of 2000 at the ripe old age of ~49-69 years! See
RAAB #1 History for further details of her life
history. Other specimens have not lived so long, but demonstrate that Rubber
Boas commonly live beyond twenty or thirty years, even in the wild.3 There are several other wild individuals that
Richard Hoyer has found every few years for at least two decades.

Habits

Rubber Boas are fossorial
(definition), or at least semi-fossorial. They do spend a lot of time
underground, but like other snakes, primarily use existing rodent tunnels or
rock fractures. The are also nocturnal/crepuscular (definition), and therefore are usually not active
during the day, and prefer to hide underground or under pieces surface cover
than bask in the open. Rubber Boas hibernate during the winter months over their
entire range, sometimes from mid October to to mid March. During Spring and Fall
they may be found under surface objects thermoregulating in the warm sun. During
Summer when the weather is warm, Rubber boas rarely are found on the surface,
and remain underground to keep cool and moist. However, given optimal
conditions, they can be found active in the summer indicating that they do not
avestate. In almost every description found of Rubber Boas, it is
mentioned that they are good swimmers. There does not seem to be a firm basis for this conclusion. Young boas are able to float, and all boas can keep their head above the water, but they are poor swimmers when compaired to some other species.

Temperament

Rubber boas are incredibly docile snakes and are ideal for handling by
children and those trying to overcome a fear of snakes. Unlike many other
snakes, they never use striking as a defense mechanism, although if handled too
roughly, they will musk the holder (excrete very smelly substance from their
vent), but absolutely will not strike in defense. Upon being picked up, a Rubber
boa will gently wrap around the holder's wrist for upwards of an hour or more
before seeking to crawl around. Even when warm and active, Rubber Boas rarely
move swiftly.

Distribution

Rubber boas can be found from as far south as the San Bernardino and San
Jacinto Mountains to the east of Los Angeles, northward in a nearly continuous
distribution to British Columbia, and eastward through Idaho, northern Nevada,
Utah, central Montana, and western Wyoming.4
There are also reports of sightings in S.W. Alberta, and N.W. Colorado. Although
seldom seen, they are usually common where the habitat is adequate,1, 3 with
population densities at least as great as 20 per hectare!8 See range map.

Native Habitat

Rubber boas can be found in a very wide range of different habitats from the
open pockets in coniferous rainforests of the Pacific Northwest to the dry arid
mountains of southern California. They generally are not as heat tolerant as
many other snakes, and disappear in warmer weather to find cooler surroundings
and moisture. In all of these habitats, Rubber Boas are not often found on top
of the ground and vegetation. They spend the vast majority of time under logs,
rocks, or underground in rock openings or rodent burrows. See
Photos Page for examples of habitat used
by Rubber Boas. See additional discussion on the
Habitat page.

Home Range

Rubber Boas appear to have a strong fidelity to a small home range where
food, cover, and warmth are adequate. Some individuals have been observed year
after year after year in the same location, or within 100 meters of last
capture.2,3 Yet there is at least some small portion of the population that
is migratory for one reason or another including excessive competition, too
dense of tree canopy growth, lack of prey, etc. Young born in the fall disperse
the following spring shortly after emergence from hibernation.3

Natural Prey

Rubber boas are slow, small snakes that primarily prey on young nestling
mammals (voles, shrews, deer mice, etc). When nestling rodents are encountered,
they will eat the entire litter if possible, deflecting any attacks from the
mother mouse with their blunt tail. Adult wild Rubber boas often have extensive
scarring on their tails. Although baby rodents are the preferred prey, they will
eat lizard and snake eggs; and to a lesser extent, lizards, baby birds, baby
bat, and there is one recorded instance of eating another snake. My personal
opinion is that the instances where another snake has been consumed is more due
to accidents than intent to eat another snake. Rubber Boas have been observed
constricting multiple prey simultaneously.3,5

Predators

Rubber Boas are vulnerable to most any carnivorous predator due to their slow
nature and lack of active defenses. Other snakes, birds of prey, Ravens,
Coyotes, Raccoons, Skunks, Moles, and Cats are only a few of the known
predators. The Rubber Boas primary defense against predatation is its secretive
nature.
It was previously thought that the reason a Rubber Boa's tail was often scarred
is due to their tendency to ball up, and use the tail as a false head when
attacked by a predator. Common reasoning though tells us that such a defense is
not useful against the predators listed above. Tail tip scarring occurs more
commonly from deflecting the attacks of a mother mouse trying to defend her nest
as the Rubber Boa consumes the nestling mice. Aggression trials have
demonstrated that a Rubber Boa, once feeding, may be undeterred by repeated
attacks from a mouse, simply holding the mouse at bay with "false strikes" of
the tail as it is flipped back and forth.

Species/Subspecies

As with many other animals, the taxonomic classification is uncertain and
debated. Paolo Emilio Botta collected the first specimen of this snake in the
19th century. In 1920, Van Denburgh, described three subspecies which was
confirmed by Klauber in 19436; Pacific
(C.b. bottae), Great Basin (C.b. utahensis), and Southern
Californian (C.b. umbratica). Initial subspecies were designated based on
scale variations noted. In 1974, the Great Basin subspecies was dropped when it
was noted that individuals in Western Oregon did not fit the guidelines
established for identification between Pacific and Great Basin subspecies.7
Initial confusion over differences occurred due to an apparent misunderstanding
of the wide variation in scale patterns between and within each locality.
In fact, each individual snake may be identified by the "fingerprint" of their
head and ventral scales unique to each snake. Scalation features can be
extremely variable within a single locale bringing into question the ability to
use such morphological traits to differentiate between subspecies of the Rubber
Boa. Some sources list utahensis as a valid subspecies, while other sources do
not. The Southern Rubber Boa subspecies is currently listed as threatened by the
CA DF&G, and therefore protected by California law (although evidence exists
that they are abundant, and range further than currently published).23 In 2001, a paper9was published in which it was proposed that the Southern Rubber Boa is a
separate species. This may be the case, but is seriously doubted by other
experts on the Rubber Boa, due to numerous errors and assumptions made in this
paper that may not be appropriate. Certain scalation features of umbratica
consistently differ from other Rubber Boas, and other morphological traits such
as diminutive size do indicate the validity of subspecies status. Further work,
building off of the mtDND work already performed may be necessary to sort all
this out.

Relatives

The closest relative to the Rubber Boa is the Rosy Boa, also native to
Western North America. In the southern most part of the Rubber Boa's range, and
the northern most part of the Rosy Boa's range, they live in the same mountain
ranges, although generally at differing elevations. There is at least one
place I am aware of where a Rosy Boa and a Rubber Boa were found to be
sympatric. See Jordan's excellent page regarding
Rosy Boas.

Sand Boas also appear to be closely related to Rubber and Rosy Boas. See
Chris's excellent site about Sand
Boas He also has devoted quite a bit of time discussing the taxonomic
relationships of these species
Here

8 - Personal observation in Spring of 2001 from one
search of 15 minutes. 12 boas found in an area of .6 hectare, or 1.5 acres.
Note: weather was unfaborable for finding Rubber Boas, yet a population of 8
per acre was found in this one short search! Density could be higher, but this
represents minimimum density at a given point in time in good habitat.